.. auto-generated by dev_tools.docs.nxdl from the NXDL source base_classes/NXaperture.nxdl.xml -- DO NOT EDIT

.. index::
    ! NXaperture (base class)
    ! aperture (base class)
    see: aperture (base class); NXaperture

.. _NXaperture:

==========
NXaperture
==========

..
    Contributors List

    .. |contrib_name| replace:: Aaron Brewster|phyy-nx|https://avatars.githubusercontent.com/u/13471434?v=4|2022-06-15

    .. |contrib_name| replace:: Pete R Jemian|prjemian|https://avatars.githubusercontent.com/u/2279984?v=4|2022-01-28

    .. |contrib_name| replace:: Peter Chang|PeterC-DLS|https://avatars.githubusercontent.com/u/1381719?v=4|2020-10-20

    .. |contrib_name| replace:: Tobias Richter|zjttoefs|https://avatars.githubusercontent.com/u/856440?v=4|2018-05-15

**Status**:

  base class, extends :ref:`NXobject`

**Description**:

  .. collapse:: A beamline aperture. ...

      A beamline aperture.

      Note, the group was incorrectly documented as deprecated, but it is not and it is in common use.

**Symbols**:

  No symbol table

**Groups cited**:
  :ref:`NXgeometry`, :ref:`NXnote`, :ref:`NXoff_geometry`, :ref:`NXtransformations`

.. index:: NXtransformations (base class); used in base class, NXoff_geometry (base class); used in base class, NXgeometry (base class); used in base class, NXnote (base class); used in base class

**Structure**:

  .. _/NXaperture@default-attribute:

  .. index:: default (file attribute)

  **@default**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    .. collapse:: Declares which child group contains a path leading  ...

        .. index:: plotting

        Declares which child group contains a path leading 
        to a :ref:`NXdata` group.

        It is recommended (as of NIAC2014) to use this attribute
        to help define the path to the default dataset to be plotted.
        See https://www.nexusformat.org/2014_How_to_find_default_data.html
        for a summary of the discussion.

  .. _/NXaperture/depends_on-field:

  .. index:: depends_on (field)

  **depends_on**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    .. collapse:: NeXus positions components by applying a set of translations and rotations ...

        NeXus positions components by applying a set of translations and rotations
        to apply to the component starting from 0, 0, 0. The order of these operations
        is critical and forms what NeXus calls a dependency chain. The depends_on
        field defines the path to the top most operation of the dependency chain or the
        string "." if located in the origin. Usually these operations are stored in a
        NXtransformations group. But NeXus allows them to be stored anywhere.

        The reference point of the aperture is its center in the x and y axis. The reference point on the z axis is the
        surface of the aperture pointing towards the source.

        In complex (asymmetic) geometries an NXoff_geometry group can be used to provide an unambiguous reference.

        .. image:: aperture/aperture.png
            :width: 40%

  .. _/NXaperture/material-field:

  .. index:: material (field)

  **material**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    Absorbing material of the aperture

  .. _/NXaperture/description-field:

  .. index:: description (field)

  **description**: (optional) :ref:`NX_CHAR <NX_CHAR>` 

    Description of aperture

  .. _/NXaperture/TRANSFORMATIONS-group:

  **TRANSFORMATIONS**: (optional) :ref:`NXtransformations` 

    .. collapse:: This is the group recommended for holding the chain of translation ...

        This is the group recommended for holding the chain of translation
        and rotation operations necessary to position the component within
        the instrument. The dependency chain may however traverse similar groups in
        other component groups.

  .. _/NXaperture/OFF_GEOMETRY-group:

  **OFF_GEOMETRY**: (optional) :ref:`NXoff_geometry` 

    Use this group to describe the shape of the aperture

  .. _/NXaperture/GEOMETRY-group:

  **GEOMETRY**: (optional) :ref:`NXgeometry` 


    .. index:: deprecated


    **DEPRECATED**: Use the field `depends_on` and :ref:`NXtransformations` to position the aperture and :ref:`NXoff_geometry` to describe its shape

    .. collapse:: location and shape of aperture ...

        location and shape of aperture

        .. TODO: documentation needs improvement, contributions welcome

            * description of terms is poor and leaves much to interpretation
            * Describe what is meant by translation _here_ and ...
            * Similar throughout base classes
            * Some base classes do this much better
            * Such as where is the gap written?


  .. _/NXaperture/BLADE_GEOMETRY-group:

  **BLADE_GEOMETRY**: (optional) :ref:`NXgeometry` 


    .. index:: deprecated


    **DEPRECATED**: Use :ref:`NXoff_geometry` instead to describe the shape of the aperture

    location and shape of each blade

  .. _/NXaperture/NOTE-group:

  **NOTE**: (optional) :ref:`NXnote` 

    describe any additional information in a note


Hypertext Anchors
-----------------

List of hypertext anchors for all groups, fields,
attributes, and links defined in this class.


* :ref:`/NXaperture/BLADE_GEOMETRY-group </NXaperture/BLADE_GEOMETRY-group>`
* :ref:`/NXaperture/depends_on-field </NXaperture/depends_on-field>`
* :ref:`/NXaperture/description-field </NXaperture/description-field>`
* :ref:`/NXaperture/GEOMETRY-group </NXaperture/GEOMETRY-group>`
* :ref:`/NXaperture/material-field </NXaperture/material-field>`
* :ref:`/NXaperture/NOTE-group </NXaperture/NOTE-group>`
* :ref:`/NXaperture/OFF_GEOMETRY-group </NXaperture/OFF_GEOMETRY-group>`
* :ref:`/NXaperture/TRANSFORMATIONS-group </NXaperture/TRANSFORMATIONS-group>`
* :ref:`/NXaperture@default-attribute </NXaperture@default-attribute>`

**NXDL Source**:
  https://github.com/nexusformat/definitions/blob/main/base_classes/NXaperture.nxdl.xml